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  1. Peter Twissell

    Bmw engine

    Certainly. I used to be on a Dnepr owners group, but it faded into obscurity and I don't do facebook.
  2. Peter Twissell

    Bmw engine

    This picture was taken a couple of years ago. See also here https://www.homemodelenginemachinist.com/threads/a-gert-big-radial.31859/
  3. Peter Twissell

    Nalon Viper 2.5cc CI Engine

    Re. Alignment of chamfers, I will either machine the chamfers on the parts after they are otherwise finished and bolted together, or make the chamfers on the end parts a bit smaller than those on the crankcase, so there is a clear intentional difference.
  4. Peter Twissell

    Ohrndorf 5 Cylinder Radial

    Thanks dieselpilot, I had wondered whether it was a trade name.
  5. Peter Twissell

    Ohrndorf 5 Cylinder Radial

    I'm not sure what is meant by "stressproof" in this context. Proof stress is a measure of the materials yield strength. When buying steel for anything with specific requirements for strength, workability, surface finish, hardening etc. it is worth looking up the available grades and their...
  6. Peter Twissell

    Ohrndorf 5 Cylinder Radial

    Nice work. I'm always amazed at how spindly some of these crank designs appear, although they are clearly up to the job. The crank for my radial is a monster by comparison.
  7. Peter Twissell

    1/20th Scale Burrell

    I made a slightly more ambitious tool for riveting. Essentially, it's a lump of steel plate with a long slot in it and a couple of tubes welded to the end, either side of the slot. One tube supports the dolly, as in Nigel's tool, the other acts as a guide for the punch, keeping it aligned to the...
  8. Peter Twissell

    1/20th Scale Burrell

    Looks just the job, scaled to an appropriate size for your engine. It's worth noting that the ram doesn't need to be a 'piston fit' in the bore, it's just acting as a displacer. Provided the seal is good, it will work.
  9. Peter Twissell

    1/20th Scale Burrell

    Hi Nigel, The second steam engine I built was a Stuart Beam Engine. I made a freelance water pump from scrap material, using balls and springs from a Triumph motorcycle oil pump for the valves. The pump ram is a section of 1/8" bright steel bar, with an O ring seal. It is only the connection to...
  10. Peter Twissell

    Steam Engine Tractor

    I think it's more Rowland Emmet than Heath Robinson.
  11. Peter Twissell

    Electronic glo-plug ignition?

    A flow plug is a resistive heater and as such, is to some degree self regulating. As the coil hearts up, it's resistance increases, limiting the current flow. I have two glow plug drivers, one of which has a NiCd cell the other has a sealed lead acid cell. Either works with all the plugs I have.
  12. Peter Twissell

    Chemotherapy just new challenge for building

    Wishing you a swift and full recovery Dave.
  13. Peter Twissell

    Steam Engine Tractor

    Splendid job and very much my kind of machine.
  14. Peter Twissell

    Electronic glo-plug ignition?

    Much of the issue described can be eliminated simply by picking the correct glow plug. I have a 4 stroke model aircraft engine which idles very slowly with a large prop and will happily keep running with no power to the plug.
  15. Peter Twissell

    Stirling engine helicopter

    I recently restored a tinplate toy helicopter, believed to be from the 1940s/50s, which works on the counterbalanced principle. It has an electric motor with simple resistor speed control and a joystick which can alter the fore/aft pitch to make it fly in circles around a central pillar, which...
  16. Peter Twissell

    Mini diesel engine.

    Some steels, generally the lower strength grades like EN8, are very difficult to achieve a good finish with. EN24 and EN16 can be finished to a mirror like condition by polishing.
  17. Peter Twissell

    Mini diesel engine.

    What materials are you using for the needle and nozzle?
  18. Peter Twissell

    Bugatti straight 8 cylinder with blower, design, 3D printed molds, castings , machining, assembly

    Ajoeiam - I am going through the same exercise. My first thought is to machine the rotors slightly oversize, then run them together with abrasive in a purpose built fixture with adjustable pitch centres. I used a similar process to make cheap steel gears fit well enough to make oil pumps.
  19. Peter Twissell

    Bugatti straight 8 cylinder with blower, design, 3D printed molds, castings , machining, assembly

    Re. Supercharger clearances: The clearance will need to be smaller in a small blower, both in proportion with the rotor diameter and because the smaller blower has a cube law capacity relationship to a larger one and a square law leakage relationship. So if the blower is simply scaled down 1:2...
  20. Peter Twissell

    Bugatti straight 8 cylinder with blower, design, 3D printed molds, castings , machining, assembly

    Hi Foketry, In my experience of this type of supercharger, i.e. positive displacement, as opposed to a turbine type, it is important that the rotors have very small clearances. When the rotors become worn, the efficiency of the blower degrades quickly to the point where it takes more power to...
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